This method was removed in Gecko 5.0 (Firefox 5.0) because its syntax differs from that of Array.slice() and String.slice(). Work is ongoing on standardizing its replacement, but for now you can use the mozSlice() method on Gecko-based browsers.

Nice.

Method was replaced by:

mozSlice – in Firefox

webkitSlice – in Google Chrome

There is one important difference in the second parameter of function:

In case of slice it was length of block that should be loaded.

In case of *Slice it is the end position of block (length + start position).